The overall objective of the proposed research is to generate a profile of the effects of acute and chronic phencyclidine (PCP) administration on complex operant behavior, primarily in patas monkeys. PCP will be compared to other abused drugs that represent its broad spectrum of CNS effects (hallucinations, stimulation, depression). The technique of repeated acquisition will be used to study drug effects on learning in individual subjects. Multiple schedules will be used in order to make a direct comparison of drug effects on learning and performance.